1. Field of the Invention
The present invention relates to a system, method, and program for initializing a storage device comprising multiple storage units through a storage controller.
2. Description of the Related Art
High end storage controllers manage Input/Output (I/O) requests from networked hosts to one or more storage devices, such as a direct access storage device (DASD), Redundant Array of Independent Disks (RAID Array), and Just a Bunch of Disks (JBOD). Storage controllers include one or more host bus adaptor (HBA) cards to communicate with one or more hosts over a network and adaptors to communicate with the storage devices.
Before the disks managed by a storage controller can be used, they must be initialized. For instance, to initialize a 524 byte sector, the storage controller would write zero data to an eight byte header at the beginning of the sector, followed by 512 bytes of zero data, followed by a two byte sequence number of the logical sector number and a two byte longitudinal redundancy code (LRC) code seeded with the physical sector number or the logical block address (LBA). This process of initializing each sector with zero data and the two byte LRC code with the seeded LBA can take up to several hours. Most prior art devices initialize disks in an array, such as a RAID array, by performing a “full stripe” write, where the storage controller writes an entire stripe of data and parity to each disk in the stripe using one write command for each sector to initialize the data in each sector of the stripe.
Many storage controllers may have to initialize numerous attached hard disk drives. For instance, in certain Fibre Channel implementations, a storage controller may connect up to 126 or so hard disk drives on a Fibre Channel Arbitrated Loop. One factor that adversely affects the initialization performance in such large arrays is the disparity in the transfer rates on the loop between the devices and the internal data transfer rate in the hard disk drives. Arbitrated loop technology supports a transfer rate of 200 megabytes per second (MB/s) and disk drives can transfer data internally at a rate of up to 15 MB/s. Such a ratio means that the storage controller can only write initialization data to seven attached disk drives before maximizing the loop throughput. Thus, the throughput of the connection between the storage controller and disk drives is a bottleneck that can substantially affect the performance of initialization in systems when there are more than 10 disk drives. In fact, in an eighty disk drive system with 2.8 terabytes of data, the initialization process can take up to ten hours to complete.
For these reasons, there is a need in the art to provide improved techniques for initializing data in a disk array.